System and method for wireless power reception

ABSTRACT

A system for wireless power reception, preferably including one or more: antennas, dynamic impedance matches, RF-DC converters, DC impedance converters, and/or DC power outputs. A method for wireless power reception, preferably including: receiving power wirelessly at an antenna, dynamically adjusting an input impedance of a dynamic impedance match coupled to the antenna, and/or delivering the power to a load.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of prior U.S. applicationSer. No. 14/865,489, filed on 25 Sep. 2015, which claims the benefit ofU.S. Provisional Application Ser. No. 62/055,283, filed on 25 Sep. 2014,each of which is incorporated in its entirety by this reference.

This application claims the benefit of U.S. Provisional Application Ser.No. 62/515,962, filed on 6 Jun. 2017, which is incorporated in itsentirety by this reference.

TECHNICAL FIELD

This invention relates generally to the wireless power field, and morespecifically to a new and useful system and for power reception in thewireless power field.

BACKGROUND

Efficient power reception can be important in wireless power systems.Thus, there is a need in the wireless power field to create an improvedsystem and method for wireless power reception.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A-1B are schematic representations of a first and secondembodiment, respectively, of the system.

FIG. 2 is a schematic view of a first example of an antenna.

FIG. 3A is a perspective view of a second example of an antenna.

FIG. 3B is a plan view of a cross resonator of the second example of theantenna.

FIG. 3C is a perspective view of an example of a split-ring resonator.

FIGS. 4A-4D are plan views of specific examples of anelectro-inductive-capacitive resonator.

FIGS. 5A-5B are schematic representations of an embodiment and aspecific example, respectively, of the dynamic impedance match.

FIGS. 6A-6B are schematic representations of an embodiment and aspecific example, respectively, of the RF-DC converter.

FIGS. 7A-7B are schematic representations of an embodiment and aspecific example, respectively, of the DC impedance converter.

FIG. 8 is a flowchart representation of an embodiment of the method.

FIGS. 9A-9D are schematic representations of various specific examplesof the dynamic impedance match.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiments of the inventionis not intended to limit the invention to these preferred embodiments,but rather to enable any person skilled in the art to make and use thisinvention.

1. Overview

A system 100 for wireless power reception preferably includes one ormore antennas 110, dynamic impedance matches 120, RF-DC converters 130,DC impedance converters 140, and/or DC power outputs 150 (e.g., as shownin FIG. 1A). The system 100 (e.g., wireless power receiver such as an RFpower receiver) preferably functions as a radio-frequency power receiverand preferably receives radio power wirelessly from a radio-frequencypower transmitter (e.g., as described in U.S. patent application Ser.No. 14/865,489, filed 25 Sep. 2015, the entirety of which isincorporated by this reference). However, the system 100 canadditionally or alternatively include any other suitable elements in anysuitable arrangement.

2. Benefits

The system 100 and/or method can confer several benefits. First, bydynamically tuning the input impedance presented to the antennas, thedynamic impedance match 120 can enable efficient reception of arbitraryRF input fields using arbitrary antennas and/or other RF power sources,and/or can detune the input impedance to limit power reception, whichcan result in a significant reflection coefficient, thereby potentiallyenabling other wireless power receivers to receive RF power that wouldotherwise be received by the system 100. For example, if the antennasare accepting more power than other elements of the system, such as theRF-DC converters, can handle, the dynamic impedance match can detuneitself so that this extra power is reflected off of the network and sentback out of the antennas. Second, by dynamically tuning the DC outputimpedance of the system, the DC impedance converter 140 can enableefficient power provision to arbitrary DC loads and/or enable efficientoperation of the RF-DC converter(s). Third, by reducing variance ininput current and/or voltage (e.g., variance arising from arbitraryand/or changing RF input fields and/or coupling between antennas), suchas variance DC current and voltage output by the RF-DC converters, aparallel-series array of system components can further increase theoverall system efficiency. However, the system 100 and/or method canadditionally or alternatively confer any other suitable benefits.

3. System 3.1 Antenna

The antenna 110 preferably functions to receive power (e.g.,electromagnetic radiation transmitted toward the system 100, preferablypropagating or “far-field” radiation but additionally or alternativelyevanescent or “near-field” radiation) and to couple the received powerinto the system 100. The antenna 110 preferably includes atightly-coupled array of resonators 111 (e.g., as shown in FIG. 3A), butcan additionally or alternatively include a loosely-coupled array, asparse array, a single resonator 111, and/or any other suitable antennaelements.

The resonators 111 preferably have a high quality factor, which canincrease power reception for a given resonator size or footprint. Theresonators 111 preferably have a large conductor thickness and a lowdielectric loss tangent. Each resonator 111 preferably outputs powerthrough a tap (e.g., conductive pin or via) at or near a currentanti-node and/or through a coupled circuit. The resonators 111 caninclude resonant loops (e.g., as shown in FIG. 2), cross-resonators(e.g., as shown in FIG. 3B), split-ring resonators (e.g., as shown inFIG. 3C), electro-inductive-capacitive resonators (e.g., as shown inFIGS. 4A-4D), other physically small resonators (e.g., small relative totheir resonance wavelength), and/or any other suitable resonators.However, the resonators can be otherwise configured.

The antenna 110 can optionally include multiple arrays (and/or otherresonator arrangements) arranged with different orientations, which canfunction to efficiently couple to radiation of different polarizations(e.g., orthogonal polarizations). In a first embodiment, the antenna 110includes parallel resonator layers (e.g., parallel resonator arrays),each layer having a different in-plane resonator orientation (e.g.,orthogonal orientations, oriented at oblique angles, etc.). In a secondembodiment, the antenna 110 includes resonators on non-parallel planes(e.g., orthogonal planes, planes oriented at oblique angles, etc.).However, the antenna 110 can additionally or alternatively include anyother suitable resonators 111 and/or other antenna elements, and canhave any other suitable arrangement. The antenna 110 can be ametamaterial or have any other suitable configuration.

The antennas of the transmitter (e.g., active antennas, passiveantennas, etc.) and/or receiver can optionally include one or moresupergaining antennas, supergaining arrays, arrays of supergainingantennas, and/or any other suitable structures capable or and/orconfigured to exhibit supergaining behavior. Supergaining structures canexhibit very high gain relative to their physical size. For example,such structures can exhibit an electrical area A_(e), defined as

${A_{e} = \frac{G\; \lambda^{2}}{4\; \pi}},$

wherein λ is the radiation wavelength and G is the antenna gain at thatwavelength, much greater that their physical area A (e.g., footprint).In a first example, in which the antenna(s) define a sub-wavelengthstructure (e.g., define a length scale less than the radiationwavelength), the structures can exhibit an aperture efficiency, definedas A_(e)/A, of 2-100 (e.g., 6.5-10, 10-15, 15-22, 22-35, less than 6.5,greater than 25, etc.) and a quality factor of 100-5,000,000 (e.g.,500-5000, 5000-50,000, 50,000-750,000, less than 500, greater than750,000, etc.). In a second example, in which the antenna(s) define asuper-wavelength structure (e.g., define a length scale greater than theradiation wavelength), the structures can exhibit an aperture efficiencyof 1-10 (e.g., 1.5-1.6, 1.6-1.7, 1.7-1.8, 1.8-1.9, 1.9-2, 2-2.15, lessthan 1.5, greater than 2.15, etc.) and a quality factor of 10-5,000,000(e.g., 50-500, 500-5000, 5000-50,000, 50,000-750,000, less than 500,greater than 750,000, etc.). However, the structures can additionally oralternatively define any other suitable aperture efficiencies and/orquality factors.

In a first variation, such structures can include one or more resonatorsdefining geometries that include sub-wavelength features (e.g., featuresdefining characteristic dimensions smaller than the wavelengths ofradiation that the resonator is configured to resonate withefficiently), such as cross-resonators (e.g., as shown in FIG. 3B),split-ring resonators (e.g., as shown in FIG. 3C), and/orelectro-inductive-capacitive resonators (e.g., as shown in FIGS. 4A-4D).In a second variation, such structures can include a discretizedaperture (e.g., array of metamaterial unit cells, such ascross-resonators, split-ring resonators, and/orelectro-inductive-capacitive resonators; example shown in FIG. 3A),wherein the discrete elements of the aperture are controlled (e.g.,independently, separately, etc.), such as to approximate a continuousdistribution across the aperture. In a third variation, such structurescan include an array of classical antenna elements (e.g., patchantennas, dipole antennas, etc.) arranged to enable and/or enhancesupergaining behavior (e.g., as described in M. T. Ivrlač and J. A.Nossek, “High-efficiency super-gain antenna arrays,” 2010 InternationalITG Workshop on Smart Antennas (WSA), Bremen, 2010, pp. 369-374, whichis hereby incorporated in its entirety by this reference).

3.2 Dynamic Impedance Match

The dynamic impedance match 120 preferably functions to efficientlycouple the antenna 110 to the downstream elements of the system (e.g.,to the RF-DC converter 130). The dynamic impedance match 120 can includean input 121, a tuning network 122, a power measurement module 123, acontrol network 124, an output 125, and/or any other suitable elements(e.g., as shown in FIGS. 5A-5B and/or 9A-9D).

The input 121 (e.g., RF power input) preferably functions to receive RFpower from a power source (e.g., the antenna 110) that can exhibitarbitrary and/or changing output impedance and/or power magnitude. Theinput 121 can be electrically coupled to (e.g., electrically connectedto, resonantly coupled to, configured to be driven by, etc.) the antenna110 and/or other power source. For example, the input 121 can beconnected to the antenna 110 by a coaxial cable. However, the input canbe otherwise coupled to the antenna.

The tuning network 122 (e.g., impedance tuning network) preferablyfunctions to tune the input impedance of the dynamic impedance match(e.g., the impedance experienced at the input 121 by the antenna 110).For example, the tuning network 122 can include a circuit including oneor more inductors and capacitors. In one example, the tuning network 122includes one or more variable electrical components (e.g., variablecapacitor), preferably wherein the control network 124 is operable toalter the electrical properties of the variable component(s) (e.g., asshown in FIGS. 5B, 9A, and/or 9D). The tuning network 122 canadditionally or alternatively include one or more switch banks (e.g., asshown in FIGS. 9B-9D), preferably controlled by the control network 124,operable to connect and disconnect certain matching components (e.g.,fixed electrical components; variable components, such as describedabove; etc.) and/or matching networks (e.g., differently-tuned T-match,pi-match, and/or L-match networks). For example, there could be a seriesof capacitors (e.g., ipF, 2 pF, 3 pF, etc.) and/or inductors attached toa switch bank. The tuning network 122 is preferably a low-pass network(e.g., wherein the one or more inductors are connected between the input121 and the power measurement module 123, and/or the one or morecapacitors are connected between the inductors and ground), but canadditionally or alternatively include a high-pass network (e.g., whereinthe one or more capacitors are connected between the input 121 and thepower measurement module 123, and/or the one or more inductors areconnected between the capacitors and ground) and/or any other suitablenetwork. The tuning network 122 can include one or more T-match,pi-match, and/or L-match networks (e.g., circuits), and can additionallyor alternatively include any other suitable reconfigurable impedancematching network(s). The tuning network 122 can be electrically coupled(preferably electrically connected) to the input 121.

The power measurement module 123 (e.g., power measurement network)preferably functions to measure the RF power coupled into the dynamicimpedance match 120 (e.g., through the tuning network 122). The powermeasurement module 123 preferably includes a power measurement moduleinput, a power output (e.g., the output 125, a power output electricallycoupled to the output 125, etc.), and a signal output. For example, thepower measurement module 123 can include a power coupler and an RF powerdetector (e.g., RSSI detector). The power coupler preferably includes aninput port (e.g., the power measurement module input), transmitted port(e.g., the power output), and coupled port, and optionally includes anisolated port and/or any other suitable ports. The power couplerpreferably transmits most power from the tuning network 122 (e.g.,received at the power coupler input port) to the transmitted port, andcouples a small portion of the power (e.g., via the coupled port) intoan RF power detector (e.g., RSSI detector), which preferably outputs apower measurement signal. The power coupler can have a coupling factor(e.g., defined as 10 log(P_(coupled)/P_(in)), wherein P_(in) is theinput power at the input port and P_(coupled) is the output power at thecoupled port) of negative 3, 6, 10, 20, 30, 3-6, 6-10, 10-20, or 20-30dB, and/or any other suitable coupling factor. The power coupler caninclude a transmission line coupler (e.g., coupled transmission lines,branch-line coupler, Lange coupler, T-junction power divider, Wilkinsonpower divider, hybrid ring coupler, etc.), a waveguide coupler (e.g.,waveguide branch-line coupler, Bethe-hole coupler, Riblet short-slotcoupler, Schwinger reversed-phase coupler, Moreno crossed-guide coupler,waveguide hybrid ring coupler, magic tee coupler, etc.), and/or anyother suitable power coupler. The RF power detector can, for example,include (e.g., be) a diode detector that outputs a rectified signal tothe control network 124 (e.g., at the signal output).

The control network 124 preferably functions to dynamically control thetuning network 122 (e.g., to optimize power coupling into the dynamicimpedance match 12 o). The control network 124 preferably implements acontrol algorithm. The control algorithm preferably includes anoptimization algorithm (e.g., single variable optimization such as aline search, multivariable optimization algorithm, etc.), but canadditionally or alternatively include any other suitable algorithms. Forexample, the control algorithm can include a power optimizationalgorithm (e.g., maximum power point tracking algorithm), such as onetypically used for photovoltaic devices (e.g., line search algorithm,perturb-and-observe algorithm, etc.). The control network 124 canoptionally include one or more compensators. In one variation, thecontrol network 124 includes: an analog-to-digital converter thatconverts the rectified signal from the diode detector into a digitalsignal, an optimization circuit that implements the control algorithmbased on the digital signal, a digital-to-analog converter that convertsthe output of the optimization circuit to an analog signal, and a bufferamplifier that outputs the analog signal to the tuning network 122,preferably via an inductive element (e.g., control network inductor)that electrically couples (e.g., connects) the buffer amplifier to thetuning network, but additionally or alternatively via any other suitableelement(s) in any suitable arrangement.

The inductance (e.g., control inductance) of the control networkinductor is preferably substantially greater than the inductance of oneor more inductive elements of the tuning network (e.g., tuning networkinductances, such as inductances of inductors of a T-match, pi-match, orL-match network), and/or the impedance of the control network inductoris preferably substantially greater than the impedance (e.g., at theincoming wave frequency) of the controlled element (e.g., controlnetwork, element of the control network such as one or more inductorsand/or capacitors, etc.). For example, the impedance of the controlnetwork inductor (and/or the control inductance) can be greater than theimpedance of the controlled element by more than a threshold amount(e.g., threshold factor, such as 1.1, 1.25, 1.5, 2, 5, 10, 20, 50, 100,200, 500, 1000, 2000, 5000, 10,000, 100,000, 1,000,000, 1-2, 2-5, 5-10,10-20, 20-50, 50-100, 100-200, 200-500, 500-1000, 1000-2000, 2000-5000,5000-10,000, 10,000-100,000, or 100,000-1,000,000 times greater, etc.;threshold absolute inductance, such as greater by more than 1, 2, 5, 10,20, 50, 100, 200, 500, 1000, 1-2, 2-5, 5-10, 10-20, 20-50, 50-100,100-200, 200-500, or 500-1000 pH, nH, μH, mH, or H, etc.). The controlinductance is preferably large enough such that its impedance at theincoming wave frequency is substantially large enough to notsignificantly affect the impedance of the controlled element. In aspecific example, the impedance of the control network inductor is atleast 10 times greater than the impedance of the controlled element.However, the control inductance and/or impedance can additionally oralternatively be equal (or substantially equal, such as within 0.1%, 1%,2%, 5%, 10%, or 25%) to one or more of the tuning network inductancesand/or impedances, substantially less than one or more of the tuningnetwork inductances and/or impedances (e.g., by more than the thresholdamount), and/or have any other suitable value.

In one example (e.g., as shown in FIG. 5B), the tuning network includesone or more inductors (e.g., inductors L1 and/or L2) and/or capacitors(e.g., capacitors C1 and/or C2). In this example, one or more of theinductors preferably electrically couples (e.g., connects) the antennato the power measurement network and the power output, and/or one ormore of the capacitors preferably electrically couples (e.g., connects)one or more of the inductors (and/or any other suitable elements, suchas the antenna, power measurement network, etc.) to ground. Such asshown in FIG. 5B, the tuning network can define a T-match network (e.g.,wherein an optional capacitor C2, which may be connected near the input121, such as at a point between the antenna 110 and the inductor L1, isabsent), a pi-match network (e.g., wherein the second inductance ofinductor L2 is substantially zero, such as zero, negligible, and/or muchless than the first inductance of inductor L1), an L-match network(e.g., wherein the optional capacitor C2 is absent and either the firstor second inductance is substantially zero), and/or any other suitabletuning network. In this example, the control network inductor L3, whichelectrically couples the control network (e.g., buffer amplifier) to thetuning network, is preferably electrically coupled (e.g., connected) tothe tuning network between at least one of the tuning network inductorsand at least one of the tuning network capacitors.

However, the control network 124 can additionally or alternativelyinclude any other suitable elements in any other suitable arrangement,and the dynamic impedance match 120 can additionally or alternativelyinclude any other suitable electrical couplings and/or connections.

3.3 RF-DC Converter

The RF-DC converter 130 preferably functions to efficiently convert RFinput power to DC output power. The RF-DC converter 130 (e.g.,rectifier) preferably includes a class-F rectifier, but can additionallyor alternatively include any other suitable rectifiers. The RF-DCconverter 130 can include an input 131, diodes 132, DC blocking filters(e.g., series DC blocking filter 133, shunt DC blocking filter 134,etc.), low pass filters 135, DC pass filters 136, outputs 137, and/orany other suitable elements (e.g., as shown in FIGS. 6A-6B).

The input 131 (e.g., rectifier input) preferably functions to receive RFpower. The input 131 can be electrically coupled to the antenna 110,preferably via the dynamic impedance match 120. For example, the input131 can be electrically connected to the output 125 of the dynamicimpedance match (e.g., by a waveguide, such as a coaxial cable,microstrip, etc.).

The diodes 132 preferably function to provide passive waveshaping (e.g.,of the input RF power). The diodes 132 can (individually and/orcooperatively) generate common-mode and/or differential-mode RF signals(e.g., harmonics of the input RF power signal). The diodes 132preferably define an antisymmetric diode pair (e.g., two diodes 132 aand 132 b with opposing orientations, one between each transmission lineand ground). The antisymmetric diode pair preferably generates oddharmonics in the common-mode signal and even harmonics in thedifferential mode signal (e.g., such that the common-mode signalapproximates a square wave). The diodes 132 can be Zener diodes,Schottky diodes, and/or any other suitable diodes or other rectifyingcomponents (e.g., transistors, thyristors, any other suitable non-linearcircuit elements and/or devices, etc.).

The RF-DC converter 130 can include series DC blocking filters 133(e.g., capacitors C3 and/or C4), shunt DC blocking filters 134 (e.g.,capacitor C5), and/or any other suitable filters. The shunt DC blockingfilter 134 preferably functions to short the differential-mode RF signal(e.g., containing substantially only even harmonics of the input RFpower signal). The DC blocking filters preferably include one or morecapacitors, and can additionally or alternatively include any othersuitable components.

The low pass filter 135 preferably functions as a harmonic terminator.The low pass filter 135 preferably does not significantly attenuate thefundamental RF signal (the input RF power signal), and preferablystrongly reflects harmonics (e.g., harmonics generated by and/orreflected off of the diodes 132 and sent back towards the input 131) ofthe fundamental (e.g., presents matched or near-matched impedance to thefundamental and high impedance to the harmonics). The low pass filter135 preferably provides a high impedance to these harmonics that aretraveling from the diodes 132 towards the input 131, and the impedancepresented to the harmonics traveling from the diodes 132 towards thefilter 135 may be substantially different than or similar to (e.g.,substantially equal to) the impedance that would be presented to theharmonics if they were travelling from the input 131 toward the filter135. The low pass filter 135 preferably includes one or more inductors(e.g., inductors L5 and/or L6), and can additionally or alternativelyinclude any other suitable components. Although described herein as alow pass filter, the low pass filter 135 can additionally oralternatively include one or more band pass filters and/or any othersuitable filters.

The DC pass filter 136 preferably functions to restrict the fundamentalRF signal (e.g., while transmitting the DC power generated by the RF-DCconverter 130). The DC pass filter 136 preferably includes one or moreinductors (e.g., inductors L3 and/or L4) and/or capacitors, and canadditionally or alternatively include any other suitable components. TheDC pass filter 136 can be electrically coupled (e.g., directlyelectrically connected) to the output 137 (e.g., rectifier output),which preferably functions to output the DC power.

3.4 DC Impedance Converter

The DC impedance converter 140 preferably functions to present asubstantially optimal load to the RF-DC converter output 137 (e.g.,regardless of an arbitrary and/or changing load at the DC power output150, such as by operating in a discontinuous conduction mode (e.g.,feedforward discontinuous conduction mode), and/or to present asubstantially consistent output to the load (e.g., standard outputvoltage, such as 3.3, 30.6, 4.5, 5, 6, 9, 12, 20, 24, 28, 36, 48, or 72V). The load can be a user device (e.g., smartphone, smartwatch, etc.),or be any other suitable powered system. The DC impedance converter 140can include an input 141, DC-DC converters (e.g., a first 142 and/orsecond switching DC-DC converter 144), DCM maintenance control 143,parameter measurement module 145, and feedback control 146 (e.g., asshown in FIGS. 7A-7B). The DC impedance converter 140 can additionallyor alternatively include an electrical energy store 147 and/or any othersuitable elements.

The input 141 preferably functions to receive DC power. The input 141can be electrically coupled (preferably electrically connected) to theRF-DC converter output 137. The input 141 preferably presents an inputimpedance substantially equal to the optimal load for the RF-DCconverter 130, but can additionally or alternatively present any othersuitable input impedance.

The DC-DC converters are preferably buck-boost converters, but canadditionally or alternatively include single-ended primary-inductorconverters (SEPIC), and/or any other suitable DC-DC converter (e.g.,buck, boost, Čuk, etc.). The DC-DC converters can include inductors(e.g., inductor L7 and/or L8), capacitors (e.g., capacitor C6 and/orC7), and/or any other suitable elements. The first switching DC-DCconverter 142 preferably operates in a discontinuous conduction mode(DCM) and/or is preferably designed to enable operation in the DCM(e.g., includes a low-value inductor, such as inductor L7), but canadditionally or alternatively operate in a continuous conduction mode(e.g., to achieve an input impedance outside a range of input impedancesachievable under DCM conditions, such as based on a feedforward and/orfeedback control). The first switching DC-DC converter 142 can beelectrically coupled (preferably electrically connected) to the input141.

The DC impedance converter 140 can optionally include a second switchingDC-DC converter 144, which preferably operates in a continuousconduction mode. The second converter 144 is preferably arrangeddownstream of the first converter 142 (e.g., wherein the first converter142 is between the input 141 and the second converter 144). However, thesecond switching DC-DC converter 144 could be omitted entirely and/orreplaced with a different subsystem that is not necessarily a DC-DCconverter. In a first variation, in which a battery is placed at theoutput of the first switching DC-DC converter 142 (e.g., instead of thesecond switching DC-DC converter 144), the output voltage of 142 issubstantially fixed to be the battery voltage. In this variation, 142would serve as a constant voltage current source that dumps charge intothe battery. In a specific example, in which the first switching DC-DCconverter 142 exhibits a converter efficiency if a battery with voltageV_(out) is placed at the output of the first switching DC-DC converter142, and an input impedance of Z_(in) is specified to be the inputimpedance of the first switching DC-DC converter 142, then the currentflowing into the battery is approximately equal to (η*V_(in)²)/(V_(out)*Z_(in)). The output voltage will be regulated by the batteryand only the current flowing into the battery will be altered topreserve the necessary converter input impedance. In a second variation,the voltage is fixed in some manner other than by a battery, such asusing a zener diode and/or a charged capacitor (e.g., an energy storageelement that can accept trickle charging). In alternative variations, alinear regulator could be used; fixing a storage element directly to theoutput of the first switching DC-DC converter 142 could be used; astandard charge controller could be used; more advanced control such asan additional DC-DC converter (e.g., converter such as described above);and/or any other suitable system (e.g., system in which strong loadregulation is not needed) could be used. The second switching DC-DCconverter 144 could additionally or alternatively function as a powerrouting network (e.g., a switch to pass power from the first switchingDC-DC converter 142 to a battery and/or some other load, etc.). However,the DC impedance converter 140 can additionally or alternatively includeany other suitable DC-DC converters in any suitable arrangement.

The DCM maintenance control 143 preferably functions to maintain thefirst switching DC-DC converter 142 in the discontinuous conductionmode. However, the DCM maintenance control 143 can additionally oralternatively function to maintain the first switching DC-DC converter142 in a continuous conduction mode (CCM), such as to achieve an inputimpedance outside a range of input impedances achievable under DCMconditions. The DCM maintenance control 143 can be electrically coupled(preferably electrically connected) to the first switching DC-DCconverter 142. In one example, the DCM maintenance control 143 includesa programmable duty cycle generator electrically connected to a controlelement (e.g., MOSFET gate) of the first switching DC-DC converter(e.g., to maintain it in a discontinuous conduction mode). The DCMmaintenance control 143 can include a feedforward control (e.g.,statically operating the duty cycle generator) and/or a feedback control(e.g., dynamically adjusting duty cycle generator operation based on DCimpedance converter operation measurements, such as based on the outputof the first switching DC-DC converter 142 and/or based on operation ofthe second switching DC-DC converter 144 and/or the associated feedbackcontrol 146). The DC impedance converter operation measurements caninclude: inductor current and/or capacitor voltage (e.g., for theinductors and/or capacitors of the first switching DC-DC converter 142,such as inductor L7 and/or capacitor C6); voltage, current, and/or poweroutput from the DC impedance converter 140 and/or the first switchingDC-DC converter 142 (e.g., wherein the control 143 is configured tooptimize for the maximum power output from the converter); and/or anyother suitable parameter measurements.

The parameter measurement module 145 preferably functions to measure oneor more parameters (e.g., voltage, current, etc.) to be regulated at theDC power output 150. The parameter measurement module 145 can beelectrically coupled (preferably electrically connected) to the secondswitching DC-DC converter 144 (e.g., at the parameter measurement moduleinput) and/or to the DC power output 150 (e.g., at the parametermeasurement module output).

The feedback control 146 preferably functions to maintain the secondswitching DC-DC converter 144 in a continuous conduction mode and/or toregulate one or more output parameters (e.g., the parameters measured bythe parameter measurement module 145). The feedback control 146 can beelectrically coupled (preferably electrically connected) to the secondswitching DC-DC converter 144 (e.g., at the feedback control output)and/or to the DC power output 150 (e.g., at the parameter feedbackcontrol input).

In one example, the feedback control 146 includes a compensator and aduty cycle generator. In this example, the compensator input iselectrically connected to the DC power output 150, and the compensatoroutput controls the duty cycle generator. Further, in this example, theduty cycle generator output is electrically connected to a controlelement (e.g., MOSFET gate) of the second switching DC-DC converter(e.g., to maintain it in a continuous conduction mode).

The DC impedance converter 140 can optionally include one or moreelectrical energy stores 147. The electrical energy store 147 canfunction to buffer DC power delivery to the load and/or to poweroperation of the DC impedance converter 140 (and/or any other suitableelements of the system, such as the control network 124), such as duringsystem startup (e.g., before wirelessly-received power is available topower the active elements of the system) and/or throughout systemoperation. In one variation, the DC impedance converter 140 can controlDC power routing between the input 141, electrical energy store 147, andDC power output 150. For example, when excess power (e.g., exceeding theload's requirements) is available, it can be routed to the electricalenergy store 147, and when the load's power demands exceed the powerfrom the input 141, the deficit can be provided from the electricalenergy store 147. The electrical energy store 147 can include one ormore batteries, capacitors (e.g., supercapacitors, capacitor C8, etc.),and/or any other suitable electrical energy storage components. In oneexample, DC power routing for the DC impedance converter is achievedthrough a load switch that is controlled by an onboard logic unit thatresponds to one or more measurements, such as battery level and/orpower, voltage, and/or current output to the energy storage elementand/or load.

The DC impedance converter 140 (and/or any other suitable elements ofthe system) can additionally or alternatively include one or morebootstrapping networks. The bootstrapping network preferably functionsto power operation of the DC impedance converter 140 (and/or any othersuitable elements of the system, such as the control network 124), suchas during system startup (e.g., before active elements of the systemhave started up and/or converged on acceptable configurations forefficient wireless power reception and/or delivery) and/or throughoutsystem operation. The bootstrapping network preferably receives (anddistributes) power from the DC impedance converter output (e.g.,analogous to an additional load), which can be beneficial as thebootstrapping network will not substantially alter the input impedance(e.g., by a possibly arbitrary and/or variable amount) at the RF-DCconverter output 137. However, the bootstrapping network canadditionally or alternatively receive (and distribute) power from theRF-DC converter output 137 and/or from any other suitable location. Inone example, during receiver startup (e.g., before the DC impedanceconverter is powered, immediately following initial reception ofsubstantial wireless power, etc.), the DC impedance converter allowspower flow from the RF-DC converter output 137 to the bootstrappingnetwork (e.g., to the electrical energy store 147, such as an outputcapacitor of the DC impedance converter), and the bootstrapping networkregulates (e.g., loosely regulates) delivery of this power to the activeelements of the DC impedance converter (e.g., DCM maintenance control143, parameter measurement module 145, and/or feedback control 146,etc.) and/or any other suitable elements of the system. Once powered bythe bootstrapping network, the active elements can achieve normaloperation of the DC impedance converter, regulating power flow from theRF-DC converter output 137 to the load and to continue powering theactive elements. However, the DC impedance converter 140 canadditionally or alternatively include any other suitable elements in anysuitable arrangement, with any other suitable electrical couplingsand/or connections.

3.5 Electrical Array

The system 100 can optionally include a plurality of some or all of thesystem elements. Including duplicate elements can enable reception ofgreater amounts of RF power (e.g., due to favorable arrangements ofmultiple antennas 110). The duplicate elements are preferablyelectrically connected in a parallel-series array (e.g., as shown inFIG. 1B), which can reduce the variance in current and/or voltageproduced by the array (e.g., compared with the variance of an element ofthe array, variance between the elements, etc.). In one embodiment, thesystem 100 includes an array of input subsystems that all feed into asingle output subsystem. In this embodiment, the input subsystems eachinclude an antenna 110, dynamic impedance match 120, and RF-DC converter130, and the output subsystem includes a single DC impedance converter140 and DC power output 150. The system 100 preferably includes only asmall number (e.g., one) of DC impedance converters 140, which cantypically be large and/or expensive. However, the system 100 can includeany suitable number of elements in any suitable arrangement.

4. Method

A method for wireless power reception preferably includes (e.g., asshown in FIG. 8): receiving power (e.g., RF radiation, such as microwaveradiation) wirelessly at an antenna, dynamically adjusting an inputimpedance of a dynamic impedance match coupled to the antenna, and/ordelivering the power to a load. The method can additionally oralternatively include rectifying the received power at a rectifier,adjusting an input impedance of a DC impedance converter coupled to therectifier, communicating information associated with system operation toa wireless power transmitter, and/or controlling wireless powertransmitter operation based on the information. However, the method canadditionally or alternatively include any other suitable elementsperformed in any suitable manner.

The method is preferably performed using (e.g., by) the system 100(e.g., as described above, such as regarding functionality, behavior,and/or use of the system elements), optionally in coordination with oneor more wireless power transmitters, but can additionally oralternatively be performed using any other wireless power receiversand/or other suitable systems. The method is preferably performed inresponse to receiving wireless power at the receiver and/or receiving arequest to receive wireless power, but can additionally or alternativelybe performed at any other suitable time.

The power is preferably received wirelessly from propagating (e.g.,“far-field”) radiation, but can additionally or alternatively bereceived from evanescent (e.g., “near-field”) radiation. The receivedradiation is preferably one or more pure-tone (or substantiallypure-tone, such as defining a bandwidth less than a threshold bandwidth)signals (e.g., which can be beneficial in embodiments that employ one ormore supergaining structures and/or other narrow bandwidth antennas),but can additionally or alternatively include any suitable signal types(e.g., in embodiments that employ wider-bandwidth antennas, inembodiments in which communication signals are transmitted along withthe power, etc.). In a first specific example, the radiation has aGHz-scale frequency (e.g., 5-10 GHz, such as 5.8 GHz and/or greater than5.8 GHz). In a second specific example, the radiation has a hundreds ofMHz-scale frequency (e.g., 100-500 MHz, such as 433 MHz and/or less than433 MHz). However, the power can additionally or alternatively bereceived in any other suitable form.

In one embodiment, the method includes (e.g., at the system 100, at oneor more subsets of the system 100, at multiple systems 100, at anothersystem, etc.): receiving power (e.g., RF power) wirelessly at anantenna; coupling all or some of the power to a power measurementnetwork via an impedance tuning network; at the power measurementnetwork, outputting a feedback signal (e.g., rectified electrical signaloutput by a diode of the power measurement network) to a control network(e.g., in response to coupling the power to the power measurementnetwork), the feedback signal indicative of a power metric associatedwith the power (e.g., amount of power coupled to the power measurementnetwork, such as the RSSI, etc.); determining a control signal (e.g., atthe control network), such as based on the feedback signal and a poweroptimization algorithm (e.g., as described above, such as regarding thecontrol network 124); outputting the control signal (e.g., at thecontrol network) to the impedance tuning network (e.g., wherein theinput impedance of the impedance tuning network is modified by therespective control signal); and/or delivering some or all of the powerto an output via the impedance tuning network. In this embodiment, theantenna can be electrically coupled to (e.g., electrically connected to,resonantly coupled to, operable to drive, etc.) the impedance tuningnetwork (e.g., via a lead, trace, wire, waveguide, resonant coupling,etc.), preferably to the input of the impedance tuning network, whereinRF input impedance (e.g., input impedance of the impedance tuningnetwork, input impedance experienced by the antenna, etc.; impedance atan RF frequency, such as the frequency of RF power received by theantenna) is adjusted based on the control signal (e.g., adjusteddirectly by the control signal, such as by injection of a control signalcurrent into the impedance tuning network and/or application of acontrol signal voltage to the impedance tuning network). Some or all ofthese method elements are preferably performed repeatedly (e.g., in aniterative loop; continuously, periodically, sporadically, in response totriggers, etc.).

Determining the control signal preferably includes implementing a poweroptimization algorithm (e.g., as described above, such as regarding thecontrol network 124), such as implemented over a series of iterations ofa portion of the method elements. For example, in an iteration of thepower optimization algorithm, the current control signal can modify theinput impedance of the impedance tuning network, thereby modifying thecoupling of power to the antenna, power measurement network, and/oroutput; the power measurement network can output an updated feedbacksignal based on the modified power coupling; and the control network candetermine (e.g., based on the algorithm) an updated control signal basedon the current control signal, the associated updated feedback signal,and preferably one or more previous control signals and associatedfeedback signals. In this manner, the control network can determine adesired feedback signal (and optionally, an associated feedback signaland/or other metric associated with the feedback signal), preferably anoptimal feedback signal (e.g., associated with the best feedback signalachieved, such as the feedback signal indicative of the greatest powercoupling).

The method can optionally include communicating information associatedwith system operation to a wireless power transmitter and/or controllingwireless power transmitter operation based on the information. Forexample, the method can include cooperation between the system and oneor more power transmitters and/or other power receivers (e.g., using awireless communication module, such as a Wi-Fi, Bluetooth, or BLE radio)to optimize power transmission (e.g., to the system, to the set of allpower receivers, etc.). For example, the system can transmit anindication of the received power (e.g., power at the antenna 110, powermeasurement module 123, DC impedance converter 140, DC power output 150,etc.). The system can transmit periodically, when requested, and/or withany other suitable timing. In one example, the system continuouslyoptimizes the dynamic impedance match(es) 120 (e.g., as a fastoptimization inner loop, such as described above regarding implementingthe power optimization algorithm), and transmits data representing theoptimized power magnitude (e.g., measured by the power measurementmodule(s) 123). In this example, the power transmitter can adjust powertransmission parameters based on the data received from the system,preferably to optimize power transmission to the system (e.g., as aslower optimization outer loop). In a second example, all of thereceiver parameters are initially set to predetermined values (e.g.,pre-calculate to be a good baseline), such as by configuring the DCimpedance converter duty cycle and/or the RF dynamic impedance match topredetermined values upon startup. Then, the transmitter optimizationloop is performed (e.g., quickly, preferably as quickly as possible) todetermine the transmission parameters, and then the receiver-sideoptimizations are performed (e.g., once, continuously, periodically,etc.) under fixed transmission parameters, which can reduce timingissues and/or complexity. However, the method can additionally oralternatively include any other suitable elements performed in anysuitable manner.

Although omitted for conciseness, the preferred embodiments includeevery combination and permutation of the various system components andthe various method processes. Furthermore, various processes of thepreferred method can be embodied and/or implemented at least in part asa machine configured to receive a computer-readable medium storingcomputer-readable instructions. The instructions are preferably executedby computer-executable components preferably integrated with the system.The computer-readable medium can be stored on any suitable computerreadable media such as RAMs, ROMs, flash memory, EEPROMs, opticaldevices (CD or DVD), hard drives, floppy drives, or any suitable device.The computer-executable component is preferably a general or applicationspecific processing subsystem, but any suitable dedicated hardwaredevice or hardware/firmware combination device can additionally oralternatively execute the instructions.

The FIGURES illustrate the architecture, functionality and operation ofpossible implementations of systems, methods and computer programproducts according to preferred embodiments, example configurations, andvariations thereof. In this regard, each block in the flowchart or blockdiagrams may represent a module, segment, step, or portion of code,which comprises one or more executable instructions for implementing thespecified logical function(s). It should also be noted that, in somealternative implementations, the functions noted in the block can occurout of the order noted in the FIGURES. For example, two blocks shown insuccession may, in fact, be executed substantially concurrently, or theblocks may sometimes be executed in the reverse order, depending uponthe functionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts, or combinations of special purpose hardware andcomputer instructions.

As a person skilled in the art will recognize from the previous detaileddescription and from the figures and claims, modifications and changescan be made to the preferred embodiments of the invention withoutdeparting from the scope of this invention defined in the followingclaims.

We claim:
 1. A method for receiving radio frequency (RF) power at areceiver comprising an antenna, an impedance tuning network, a powermeasurement network, and a control network, the method comprising: atthe antenna, receiving RF power, wherein the antenna is electricallycoupled to an RF power input of the impedance tuning network, the RFpower input associated with an RF input impedance; coupling the RF powerto the power measurement network via the impedance tuning network; inresponse to coupling the RF power to the power measurement network, atthe power measurement network, outputting a feedback signal to thecontrol network, the feedback signal indicative of a power metricassociated with the RF power; at the control network, determining acontrol signal based on the feedback signal and a power optimizationalgorithm; at the control network, outputting the control signal to theimpedance tuning network, wherein the RF input impedance of theimpedance tuning network is modified by the control signal; anddelivering a portion of the RF power to an RF output via the impedancetuning network.
 2. The method of claim 1, further comprising, before theRF input impedance is modified, determining the control signal byperforming an optimum search, comprising, for each of a series of searchiterations: at the power measurement network, outputting a respectivefeedback signal to the control network, the respective feedback signalindicative of a respective power metric associated with the RF power; atthe control network, determining a respective control signal based on aprevious feedback signal, a previous control signal, the respectivefeedback signal, and the power optimization algorithm; and at thecontrol network, outputting the respective control signal to theimpedance tuning network, wherein the RF input impedance is modified bythe respective control signal; wherein the control signal is selectedfrom the respective control signals based on the respective feedbacksignals.
 3. The method of claim 2, further comprising: at a transmitter,throughout a first time period, transmitting RF power based on a firsttransmission configuration, wherein the receiver performs the optimumsearch during the first time period; after outputting the controlsignal, at the receiver, determining a metric associated with the RFpower; based on the metric, determining a second transmissionconfiguration; at the transmitter, in response to determining the secondtransmission configuration, throughout a second time period,transmitting RF power based on the second transmission configuration; atthe receiver, during the second time period, determining a secondcontrol signal by performing a second optimum search during the secondtime period; and in response to determining the second control signal,at the control network, outputting the second control signal to theimpedance tuning network, wherein the RF input impedance of theimpedance tuning network is modified by the second control signal. 4.The method of claim 3, wherein: the receiver further comprises arectifier and a DC impedance converter; and the method furthercomprises: at the rectifier, converting the portion of the RF power toDC power; delivering a portion of the DC power from the rectifier to aDC power output via the DC impedance converter; while delivering theportion of the DC power to the DC power output, at the DC impedanceconverter, controlling a DC input impedance of the DC impedanceconverter to optimize the portion delivered to the DC power output; anddetermining the metric, wherein the metric is indicative of powerdelivery to the DC power output.
 5. The method of claim 1, wherein thealgorithm comprises a line search algorithm.
 6. The method of claim 1,wherein the impedance tuning network comprises: an inductor electricallycoupling the antenna to the power measurement network and the poweroutput; and a capacitor electrically coupling the inductor to a ground.7. The method of claim 6, wherein: the control network comprises acontrol network inductor; the control network inductor is electricallycoupled to the impedance tuning network between the inductor and thecapacitor, wherein the control signal is output via the control networkinductor; and a control inductance of the control network inductor isgreater than a first inductance of the inductor by more than a thresholdamount.
 8. The method of claim 1, further comprising, in response todelivering the portion of the RF power to the power output: receivingthe portion of the RF power at a rectifier of the receiver; at therectifier, converting the portion of the RF power to DC power; anddelivering the DC power to a rectifier output.
 9. The method of claim 8,further comprising, in response to delivering the DC power to therectifier output: receiving the DC power at a DC impedance converter ofthe receiver; delivering a portion of the DC power to a DC power outputvia the DC impedance converter; and while delivering the portion of theDC power to the DC power output, at the DC impedance converter,controlling a DC input impedance of the DC impedance converter.
 10. Themethod of claim 9, further comprising, while delivering the portion ofthe DC power to the DC power output, powering the DC impedance converterusing a second portion of the DC power, wherein the second portionpasses through the DC impedance converter together with the portion. 11.The method of claim 9, wherein controlling the DC input impedancecomprises operating a first DC-DC converter of the DC impedanceconverter in a discontinuous conduction mode.
 12. The method of claim11, wherein controlling the DC input impedance further comprises, whileoperating the first DC-DC converter of the DC impedance converter in thediscontinuous conduction mode, operating a second DC-DC converter of theDC impedance converter in a continuous conduction mode.
 13. A radiofrequency (RF) power receiver comprising: an antenna; an impedancetuning network comprising: an RF power input electrically coupled to theantenna, wherein the RF power input is associated with an RF inputimpedance; a tuning network output electrically coupled to the RF powerinput; and a control input electrically coupled between the RF powerinput and the tuning network output; a power measurement networkcomprising: a power coupler comprising an input port, a transmittedport, and a coupled port, wherein the input port is electricallyconnected to the tuning network output; and an RF power detectorcomprising a detector input and a signal output, the detector inputelectrically coupled to the coupled port; a control network comprising:a control network input electrically connected to the signal output; anda control network output electrically coupled to the control input ofthe tuning network, wherein the control network is configured to outputa control signal at the control network output, thereby modifying the RFinput impedance of the impedance tuning network; and an electrical loadelectrically coupled to the transmitted port.
 14. The RF power receiverof claim 13, wherein the impedance tuning network further comprises: aninductor electrically coupling the RF power input to the tuning networkoutput; and a capacitor electrically coupling the inductor to a ground.15. The RF power receiver of claim 14, wherein: the control input iselectrically coupled between the inductor and the capacitor; the controlnetwork comprises a control network inductor electrically coupled to thecontrol input; and a control inductance of the control network inductoris greater than a first inductance of the inductor by more than athreshold amount.
 16. The RF power receiver of claim 13, wherein thecontrol network is configured to implement a power optimizationalgorithm based on the control network input to control the controlnetwork output.
 17. The RF power receiver of claim 13, furthercomprising: a rectifier comprising a rectifier output and a rectifierinput electrically coupled to the transmitted port; and a DC impedanceconverter comprising: a DC impedance converter input electricallycoupled to the rectifier output; a first buck-boost converter; adiscontinuous conduction mode maintenance control electrically coupledto the first buck-boost converter; a second buck-boost converter; afeedback control electrically coupled to the second buck-boostconverter; and a DC impedance converter output electrically coupled tothe DC impedance converter input via the first and second buck-boostconverters; wherein the electrical load is electrically coupled to thetransmitted port via the DC impedance converter output.
 18. RF powerreceiver of claim 17, wherein the rectifier further comprises anantisymmetric diode pair electrically coupling the rectifier input andthe rectifier output to a ground.
 19. The RF power receiver of claim 17,further comprising a first and second plurality of receiver modules,wherein: each receiver module of the first and second pluralitiescomprises a respective antenna, a respective impedance tuning network, arespective power measurement network, a respective control network, anda respective rectifier comprising a respective DC output; a firstreceiver module of the first plurality comprises the antenna, theimpedance tuning network, the power measurement network, the controlnetwork, and the rectifier; the respective DC outputs of the receivermodules of the first plurality are electrically connected in series to afirst rectified output; the respective DC outputs of the receivermodules of the second plurality are electrically connected in series toa second rectified output; and the first and second rectified outputsare connected in parallel to the DC impedance converter input.
 20. TheRF power receiver of claim 13, further comprising a supergainingstructure, wherein the supergaining structure comprises the antenna. 21.The RF power receiver of claim 13, wherein the antenna comprises anarray of tightly-coupled resonators.